Alexander wilford hall



(No Model.)

A. W. HALL.

MEUHANIGAL TELEPHONE.

No. 398,507. Patented Feb. 26, 1889 ment of the diaphragm of a mechanical tele- UNITED STATES PATENT Drains.

ALEXANDER lVILFOBD HALL, OF NEW YORK, N. Y,

MECHANICAL TELEPHONE.

SPECIFICATION forming part of Letters Patent No. 398,507, dated February, 26, 1889.

Application filed May 8, 1888. $eria1No.273,239. (No modeld To aZZ whom it may concern.-

Be it known that I, ALEXANDER WILFORD HALL, of the city and county of New York, in i the State of New York, have invented a new and useful Improvement in Mechanical Telephones, of which the following is a specification.

My invention has for its object the adjustphone to the tension most desirable for the transmission of the sound of the human voice.

I will first describe the improvement with reference to the drawings, and afterward point out the novelty in a claim.

Figure 1 in the drawings is a face view of a mechanical telephone, and Fig. 2 a transverse central sectional view in the line .ra" of Fig. 1.

Similar letters of reference designate corresponding parts in both figures.

A designates the base of the telephone, consisting of a board having an opening, a in the center, and having secured to its face a ring, 0, of metal or other material, for supporting the diaphragm Z). This ring 0 is loosely surrounded by two metal rings or hoops, 1' 1", between which the outer edge of the diaphragm Z), preferably made of some kind of a strong skin, is securely clamped and fastened by bolting these two metal rings together by screw-bolts g, passing through both rings and the diaphragm and fitted with nuts 9. The adjustment of the tension of the diaphragm is effected by means of screws 6, passing through holes in the rings "i 2" between the clamping bolts g and screwing into the base-board A. The screws a draw the diaphragm down over the outer edge of the diaphragm-supporting rings 0, thus providing for obtaining a tension best adapted for the transmission of the sounds of the human voice.

f designates a dome-like cover, made of sheet metal, having a sunk central opening, f, concentric with the diaphragm. This cover is secured to the diaphragm-supportin g rings 0 by screws 72, passing through slits 71, made in the diaphragm, as shown in Fig. 1, where the cover fis shown as having a portion broken away to expose a partof the diaphragm and one of the slits h to view. These slits 7i are 1 made radially across the upper surface of the l diaphragm-supporting rings 0, and are for the i j base-board.

purpose of enabling the tension of the diaphragin to be renewed from time to time.

should it become slack from use.

By providing for the adjustment of the tension of the diaphragm I overcome one of the principal defects of the mechanical telephones heretofore used.

I will now describe means of protecting the diaphragm against being torn out by the strain of the wire while stretching the latter in setting up the telephone, or in subsequent ad justment or repair.

(I designates a wire or cord. preferably a 1 piece of heavy catgut string. having its ends secured to the points of two set-sercws, 2' I", which screw through bracket-like supports 1' r secured to the covet-f. This cord passes through the head of a screw, 0, which passes 1 through the center of the diaphragm and is clamped thereto by means of a nut, s, screwing onto the said screw at the back of the diaphragm, and a washer, s, placed behind the head of the screw in front of the diaphragm. The head of the screw (r-being a little back of the points of the screws '1 r, the stretching of the cord produced by the turning back of said screw produces a tension on the diaphragm in opposition to the strain of the line-wire, which is connected with the diaphragm 011 the opposite side. In order that the tension of the supporting-cord (Z may be increased or relaxed without twisting or untwisting the said cord, the screw 2' has a right-handthread and the screw '2" a left-hand thread. In applying tension to the cord d, or adjusting the tension thereof, the two screws are taken hold of by the two hands of the adjuster and both turned uniformly in one direction or the other, as maybe required. The connection of the line-wire with the diaphragm is shown in Fig. 2. This is made by means of a graduated elbow-lever, or, having arms of unequal length and working on the fulcrum n in a bracket,

. a, which is secured to the base-board A, the

said lever working through aslot, (1, in the The line-wire r is represented as connected with the shorter arm of the lever 72 at a very short distance from its fulcrum, and the longer arm of the lever is represented as connected at its extremity through the link t and screw (1. The lever is represented as having a series of holes, 3, in its shorter arm to provide for the line-wire o being connected with it at different distances from the fulcrum 'n. The HHG-WiPQiHStBfl'J of being connected with the shorter arm of the lever, may be connected With the longer arm, but always nearer the fulcrum than the connection of the diaphragm. This longer arm is shown as provided with a series of holes, 4, to enable the line-Wire to be connected with it at different distances from the fulcrum.

By the employment of the lever-connection between the diaphragm and line-Wire, and making the connection of the line-wire nearer the fulcrum of the lever, I am enabled to employ a diaphragm much thinner and more sensitive to vocal vibration than has before been used in mechanical telephones. The lever-connection also gives as one of its advantages ready means of getting the line-Wire out of the building into the street, as it obviates the necessity of runningthe line-wire directly away from the center of the diaphragm any distance, and of making abrupt angles in the Wire at a short distance from the diaphragm and thereby interfering With its free vibration. It is found by practice that the first angles of the line-wire after leaving the telephone should be as far as possible from the diaphragm, Whatever angles may occur on the line. By the employment of an elbowlever the line-wire may be run directly up through the floors above and out at the roof, Where its first angle may occur; or by giving the instrument a quarter-turn on its axis the Wire may be run horizontally on the Wall through partitions and adjoining rooms before making its exit and acquiring its first angle; or the instrument may be turned on its axis to such a position that the line-Wire may pass vertically down through the floors with like advantage.

Should it be desirable to run the line directly away from the plane of the diaphragm, the graduated lever may be used with the same advantage of reduction of strain on the diaphragm by connecting the Wire with one or other of the holes 4, according to the degree of leverage needed.

What I claim as my invention, and desire to secure by Letters Patent, is

The combination, With the base A, the diaphragm-su pporting ring a, and the diaphragm b, of the diaphragm-clamping rings 'i i, and their clamping-screws'g, and the tension-adjusting screws e, applied to said clampingrings and base, substantially as and for the purpose herein described.

ALEXANDER \VILFORD HALL.

Witnesses:

FREDK. HAYNES, MINERT LINDEMAN. 

